Determining branching points of hollow organs plays an important role in determining a center line through the hollow organ, which line in turn constitutes a central component in the analysis of the hollow organs. Thus, these days, the interior of hollow organs, for example intestines or blood vessels, are visualized using the so-called virtual flight. In the process, a particular challenge is to set the center line precisely in the center within the lumen of the hollow organ.
This is particularly important in angiography, for example in computed tomography angiography (CTA), which enables the detection of deformations of vessels, e.g. stenoses or aneurysms. This is because in this case it is necessary for the dimensions of the lumen, that is say in particular the cross sections or radii of the vessels, to be precisely measured as precisely as possible such that a user can draw conclusions in respect of the type and degree of the deformation from these specifications. The precise measurement in turn requires the extent of the lumen to be measured perpendicularly with respect to the vessel profile because otherwise there could be erroneous interpretations with grave consequences. The vessel profile is in turn represented by the center line of the hollow organ and so the latter must be determined as precisely as possible.
The center lines of hollow organs are currently determined using different, graph-based methods. They are usually based on the A* algorithm or Dijkstra's algorithm, wherein the image data of the hollow organ is interpreted as a graph and, in the process, voxels are considered to be nodes with six further voxels being in the direct three-dimensional neighborhood thereof. These are inserted into the graph by being connected by edges. Using a cost function based on local grayscale values of CT image data, the weighting of the individual edges is identified and the costs for reaching a target point are determined on the basis of an underlying heuristic.
This method does not consider any knowledge relating to the geometry of the hollow organ. As a result of this, erroneous segmentations can occur within the scope of the method, particularly if the hollow organ is observed in a region in which other hollow organs or bone structures are situated in the vicinity. However, in particular, it is not possible for a distinction to be made between unbranched and branching regions of the hollow organ.